1. Field of the Invention
This invention relates to composite panels and methods for their preparation and is more particularly concerned with panels having an inner core utilizing comminuted scrap plastic material and with methods for their preparation.
2. Description of the Prior Art
One of the side effects of the startling growth of the plastics industry, particularly in recent years, has been the creation of a problem of considerable magnitude, namely, that of disposing of the vast quantities of scrap plastic material which are being generated. For example, the present trend in the automotive industry is to replace as much of the metal structural parts as possible with synthetic plastics and this is exacerbating the waste disposal problem. Disposal of plastic scrap in landfill operations is becoming less and less possible or desirable and attention is being turned to economically feasible ways in which to utilize or recycle the scrap material.
Illustratively, a number of ways of recovering useful polyols from scrap polyurethane have been described; see, for example, U.S. Pat. No. 3,738,946 and the prior art which is discussed therein. Recovery and recycling of polyvinylchloride and like plastics is also receiving considerable attention; see, for example, U.S. Pat. No. 3,836,486.
Numerous references are made in the literature to the recovery and incorporation of scrap plastic material as an inert filler in a variety of products. One of the fields in which such types of recycling has been explored is that of formation of particle board. Illustratively, Japanese Kokoku No. 1183/80 describes the incorporation of ground glass fiber waste into particle board. German OLS No. 2447174 describes the continuous poduction of insulating panels and the like using granulated scrap rubber and like waste. Japanese Kokoku No. 34972/51 describes the preparation of fiberboard from material which has been obtained by crushing urban waste with water, separating the metal, glass, stone and large particles therefrom, and recovering fibrous waste which contains plastic film waste and wood waste. The fibrous material so obtained is used as the core of a laminate which is compressed using heat and pressure to form a fibrous board.
To the best of the present Applicant's knowledge it has not previously been recognized that the physical properties of particle boards can be significantly improved by incorporating therein, as an inner core, scrap plastic which has been comminuted to particle size which will be described below. It is believed that the present invention represents not only a highly useful manner in which to employ waste scrap plastic, but provides a method of upgrading the properties of particle boards.